Ruby GC and finalizers

gistfile1.rb

# encoding: utf-8

class Bar
  def initialize(name)
    @name = name
  end

  def hi
    puts "HI #{@name}"
  end
end

class Foo
  def initialize(bar)
    @bar = bar
  end

  def hi
    @bar.hi
  end
end

module Baz
  def self.make_foo
    bar = Bar.new('kept')
    ObjectSpace.define_finalizer(bar, Baz.killed_a_bar('kept'))
    Foo.new(bar)
  end

  def self.do_bar
    bar = Bar.new('ephemeral')
    bar.hi
    ObjectSpace.define_finalizer(bar, Baz.killed_a_bar('ephemeral'))
    nil
  end

  def self.killed_a_bar(name)
    proc { puts "#{name} DIED"}
  end
end

Baz.do_bar
foo = Baz.make_foo
foo.hi

puts 'DOING GC'
GC.start

puts 'GC DONE'
sleep(1)
foo.hi


### OUTPUT
#$ ruby gc_test.rb
#HI ephemeral
#HI kept
#DOING GC
#ephemeral DIED
#GC DONE
#HI kept
#kept DIED